1. Field of the Invention
The present invention relates to a process for manufacturing a fluid jetting apparatus, and more particularly, to a process for manufacturing a fluid jetting apparatus of a print head employed in output apparatuses such as an ink jet printer, a facsimile machine, etc., to jet fluid through a nozzle.
2. Description of the Related Art
A print head is a part or a set of parts which are capable of converting output data into a visible form on a predetermined medium using a type of printer. Generally, such a print head used for an ink jet printer, and the like, uses a fluid jetting apparatus which is capable of jetting a predetermined amount of fluid through a nozzle to an exterior of a fluid chamber holding the fluid by applying a physical force to the fluid chamber.
According to methods for applying a physical force to the fluid within the fluid chamber, a fluid jetting apparatus is roughly grouped into a piezoelectric system and a thermal system. The piezoelectric system pushes out ink within the fluid chamber through a nozzle through an operation of a piezoelectric element which is mechanically expanded in accordance with a driving signal. The thermal system pushes the fluid through the nozzle by means of bubbles which are produced out of the fluid within the fluid chamber by the heat generated by an exothermic body. Recently, also, a thermal compression system has been developed, which is an improved form of the thermal system. The thermal compression system jets the fluid by driving a membrane by instantly heating a vaporizing fluid which acts as working fluid.
FIG. 1 is a vertical sectional view of a fluid jetting apparatus according to a conventional thermal compression system. A fluid jetting apparatus of the thermal compression system includes a heat driving part 10, a membrane 20, and a nozzle part 30.
A substrate 11 of the heat driving part 10 supports the heat driving part 10 and the whole structure that will be constructed later. An insulated layer 12 is defused on the substrate 11. An electrode 14 is a conductive material for supplying an electric power to the heat driving part 10. An exothermic body 13 is a resistive material having a predetermined resistance for expanding a working fluid by converting electrical energy into thermal energy. Working fluid chambers 16 and 17 contain the working fluid, to maintain the pressure of the working fluid which is expanded by heat, are connected by a working fluid introducing passage 18, and are formed with a working fluid barrier layer 15.
Further, the membrane 20 is a thin diaphragm which is adhered to an upper portion of the working fluid barrier layer 15 and the working fluid chambers 16 and 17 are moved upward and downward by the pressure of the expanded working fluid. The membrane 20 includes a polyimide coated layer 21 and a polyimide adhered layer 22.
Jetting fluid chambers 37 and 38 are chambers, formed to enclose the jetting fluid, which are designed to jet the fluid only through a nozzle 35 formed in the nozzle plate 34 when the pressure transmitted through the membrane 20 is applied to the jetting fluid. The jetting fluid is the fluid which is pushed out of the jetting fluid chambers 37 and 38 in response to the driving of the membrane 20, and finally jetted to the exterior. A jetting fluid introducing passage 39 connects the jetting fluid chambers 37 and 38. The jetting fluid chambers 37 and 38 and the jetting fluid introducing passage 39 are formed in a jetting fluid barrier layer 36. The nozzle 35 is an orifice through which the jetting fluid which is held using the membrane 20 and the jetting fluid chambers 37 and 38 is emitted to the exterior. Another substrate 31 of the nozzle part 30 is temporarily employed for constructing the nozzle part 30, and the substrate 31 of the nozzle part 30 should be removed before the nozzle part 30 is assembled.
A process for manufacturing the fluid jetting apparatus according to the conventional thermal compression system will be described below.
FIG. 2 shows a process for manufacturing a fluid jetting apparatus according to a conventional roll method.
As shown in FIG. 2, a nozzle plate 34 is transferred from a feeding reel 51 to a take-up reel 52. In the process of transferring the nozzle plate 34 from the feeding reel 51 to the take-up reel 52, a nozzle is formed on the nozzle plate 34 by laser processing equipment 53. After the nozzle is formed, air is jetted from an air blower 54 so as to eliminate extraneous substances attached to the nozzle plate 34. Next, an actuator chip 40 is bonded with the nozzle plate 34 by a tab bonder 55, and accordingly, the fluid jetting apparatus is completed. The completed fluid jetting apparatuses are wound around the take-up reel 52 to be preserved, and then sectioned in pieces in the manufacturing process for the print head. Accordingly, each piece of the fluid jetting apparatuses is supplied into the manufacturing line of a printer.
FIGS. 3A and 3B are views for showing a process for manufacturing the heat driving part and FIG. 3C is a view for showing a process for manufacturing the membrane on the heat driving part of the conventional fluid jetting apparatus. FIGS. 4A to 4C are views for showing a process for manufacturing the nozzle part.
In order to manufacture the conventional fluid jetting apparatus, the heat driving part 10 and the nozzle part 30 should be manufactured separately. Here, the heat driving part 10 is completed as the separately-made membrane 20 is adhered to the working fluid barrier layer 15 of the heat driving part 10. After that, by reversing and adhering the separately-made nozzle part 30 to the membrane 20, the fluid jetting apparatus is completed.
FIG. 3A shows a process for diffusing the insulated layer 12 on the substrate 11 of the heat driving part 10, and for forming the exothermic body 13 and the electrode 14 on the insulated layer 12 in turn. Referring to FIG. 3B, the working fluid chambers 16 and 17 and the working fluid introducing passage 18 are formed by an etching process of the working fluid barrier layer 15 through a predetermined mask patterning. More specifically, the heat driving part 10 is formed as the insulated layer 12, the exothermic body 13, the electrode 14, and the working fluid barrier layer 15 are sequentially laminated on the substrate 11 (which is a silicon-substrate). The working fluid chambers 16 and 17 which are filled with the working fluid to be expanded by heat, are formed on the etched portion of the working fluid barrier layer 15. The working fluid is introduced through the working fluid introducing passage 18.
FIG. 3C shows the separately-made membrane 20 being adhered to the upper portion of the completed heat driving part 10. The membrane 20 is a thin diaphragm, which is to be driven in a direction of the jetting fluid chamber 37 (see FIG. 1) by the working fluid which is heated by the exothermic body 13.
FIG. 4A shows a process for forming the nozzle 35 by the laser processing equipment 53 after an insulated layer 32 and the nozzle plate 34 are sequentially formed on a substrate 31 of the nozzle part 30. FIG. 4B shows a process for forming a jetting fluid barrier layer 36 on the upper portion of the construction shown in FIG. 4A, and then for forming the jetting fluid chambers 37 and 38 and the fluid introducing passage 39 (see FIG. 1) by an etching process through a predetermined mask patterning. FIG. 4C shows a process for exclusively removing the nozzle plate 34 from the conductive layer 32 and the substrate 31 of the nozzle part 30. The nozzle part 30 includes the jetting fluid barrier layer 36 and the nozzle plate 34. On the etched portion of the jetting fluid barrier layer 36, the jetting fluid chambers 37 and 38 which are filled with the fluid to be jetted and the fluid introducing passage 39, are formed. The jetting fluid such as an ink, or the like, is introduced through the jetting fluid introducing passage 39 (see FIG. 1). The nozzle 35 is formed on the nozzle plate 34 to be interconnected with the jetting fluid chamber 37, so that the fluid is jetted out through the nozzle 35. The nozzle part 30 is manufactured by the processes that are shown in FIGS. 4A to 4C. First, the nozzle plate 34 inclusive of the nozzle 35, is formed on the substrate 31 having the insulated layer 32 through an electroplating. Next, the jetting fluid barrier layer 36 is laminated thereon, and the jetting fluid chambers 37 and 38 and the jetting fluid introducing passage 39 are formed through a lithographic process. Finally, as the insulated layer 32 and the substrate 31 are removed, the nozzle part 30 is completed. The completed nozzle part 30 is reversed, and then adhered to the membrane 20 which has been pre-assembled with the heat driving part 10. More specifically, the jetting fluid barrier layer 36 of the nozzle part 30 is adhered to the polyimide coated layer 21 of the membrane 20.
The operation of the fluid jetting apparatus according to the thermal compression system will be described below with reference to the construction shown in FIG. 1.
First, an electric power is supplied through the electrode 14, and an electric current flows through the exothermic body 13 which is connected to the electrode 14. In such a situation, the exothermic body 13 generates a heat due to its resistance. The fluid within the working fluid chamber 16 is subjected to a resistance heating, so that the fluid starts to vaporize when the temperature thereof exceeds a predetermined temperature. As the fluid vaporizes more and more due to the heat, the vapor pressure accordingly increases. As a result, the membrane 20 is driven upward. More specifically, as the working fluid undergoes thermal expansion, the membrane 20 is pushed upward toward the direction indicated by the arrow in FIG. 1. As the membrane 20 is pushed upward, the fluid within the jetting fluid chamber 37 is jetted to the exterior through the nozzle 35.
Then, when the supply of electric power is stopped, the heat from the exothermic body 13 is no longer generated. Accordingly, the fluid within the working fluid chamber 16 is cooled to a liquid state, so that the volume thereof decreases and the membrane 20 recovers its original shape.
Meanwhile, a conventional material of the nozzle plate 34 is mainly made of nickel, but the trend in using a polyimide synthetic resin has increased recently. When the nozzle plate 34 is made of the polyimide synthetic resin, it is fed by a reel type. The fluid jetting apparatus is completed by the way in which a chip is bonded on the nozzle plate 34 fed in the reel type.
With the conventional fluid jetting apparatus, however, since the nozzle plate and the jetting fluid barrier layer should be separately formed during the manufacturing process of the nozzle part, numerous complex processes are required. As a result, the productivity thereof is decreased. Further, if the conventional electroplating method is employed, pressures are not uniformly exerted over the whole area of the substrate due to the uneven thickness, and also due to the technical problems in forming the jetting fluid chambers. Also, according to the conventional system, since the heat driving part-membrane assemblies, and the nozzle parts have to be sectioned in pieces into the respective units to be attached to each other, productivity decreases and the reliability deteriorates.